A feline homeobox-containing DNA sequence was isolated from the genomic library of the domestic cat using mouse homeobox Hox-3.1 as a probe. The isolated homeobox was named cat Hox-3.1. Using a panel of rodent x domestic cat somatic cell hybrids, cat Hox-3.1 was assigned to cat chromosome B4. Interestingly, it has been known that cat chromosome B4 shows syntenic homology with mouse chromosome 15 and human chromosome 12, where mouse Hox-3.1 and human Hox-3.1 have been mapped, respectively. This result affirms the linkage conservation of the Hox-3.1-containing group in three mammalian orders. At present, nucleotide sequence analysis of the cat Hox-3.1-containing region is proceeding.